Re: '83 Jason 35- stainless bolts in the bilge.
A grounding plate is a piece of metal that is in contact with water to provide the lightning with an easy path to neutral (ground).
On my Seafarer it is about 6" X 12" copper and has two bolts that go through the hull that is used to connect the rigging to it. It should have a heavy copper wire from each of the chainplates to the connections on the grounding plate.
Seafarer 29 KCB